What would you do if you wouldn't hit on the turn? Would you still 2nd barrel it?

I think he is never folding Qx, FD. Also if the flush completes, he is not folding even weak flush. If turn is not a K or A, then he should not fold 99-JJ. I can make fold some weak pairs and high cards. but high cards he should fold even on flop, because on such flops they are scared by made flushes. So I think he mostly has Qx and FD. So I think we cannot bet turn.

What would you do if you wouldn't hit on the turn? Would you still 2nd barrel it?

I think he is never folding Qx, FD. Also if the flush completes, he is not folding even weak flush. If turn is not a K or A, then he should not fold 99-JJ. I can make fold some weak pairs and high cards. but high cards he should fold even on flop, because on such flops they are scared by made flushes. So I think he mostly has Qx and FD. So I think we cannot bet turn.